Users of an electrical power system expect a reliable power supply therefrom and there are various ways for ensuring an un-interrupted operation of the electrical power system. For example, the electrical power system should be designed so that even if its largest single power generation source is lost, the overall balance between electricity production and consumption should still be kept.
A loss of a generation source in the electrical power system will cause the system frequency to drop. Other power generation sources may increase their production to compensate for the lost generation source's power contribution to the power generation. In order to recover the electrical power system to a stable situation and thereby avoid service interruption, other conventional energy generation sources thus have to be engaged. Such sources, e.g. gas turbines, diesel engines, steam turbines, hydro power etc., need a start-up time and have limitations in reliability. For example, thermal power plants respond relatively slowly due to difficulty to increase temperatures fast enough in boilers without putting mechanical stress upon them. Other power generation sources have other limitations, e.g. gas turbines, although having fast response times, have lower efficiency and thus higher production costs.
In view of the above, it would be desirable to improve the handling of frequency disturbances when bridging over between an initial frequency drop and steady state following a recovery.